Dynamo-electric machines

ABSTRACT

A rotor winding for a cylindrical air-gap dynamo-electric machine which winding is of concentric coil form wound on a rotor core formed of magnetic material, each coil having slot embedded portions disposed in axially extending slots formed in the rotor core and end-connecting portions disposed beyond the ends of the slots, one or more conductors forming a coil being modified in shape where the extension from a slot embedded portion to an endconnecting portion occurs in such a way that the radial depth of at least part of the end-connecting portion is less than the radial depth of the slot embedded portion.

United States Patent 91 Easton DYNAMO-ELECTRIC MACHINES Vivian Easton,Tyne, England [75] Inventor: Newcastle-upon- [73] Assignee: ReyrolleParsons Limited, Durham,

England [22] Filed: July 13, 1970 [21] Appl. No.: 54,133

[30] Foreign Application Priority Data July 16, 1969 Great Britain..3588l/69 [56] References Cited UNITED STATES PATENTS 3,176,176 3/1965Willyoung ..3l0/270 X 8/1971 Guimbal ..310/6l 8/1910 Smoot ..3l0/262Primary Examiner-D. F. Duggan Attorney-Holman & Stern 5 7 1 ABSTRACT Arotor winding for a cylindrical air-gap dynamo-electric machine whichwinding is of concentric coil form wound on a rotor core formed ofmagnetic material, each coil having slot embedded portions disposed inaxially extending slots formed in the rotor core and end-connectingportions disposed beyond the ends of the slots, one or more conductorsforming a coil being modified in shape where the extension from a slotembedded portion to an end-connecting portion occurs in such a way thatthe radial depth of at least part of the end-connecting portion is lessthan the radial depth of the slot embedded portion.

2 Claims, 10 Drawing Figures SHEET 2 [IF 5 v PATENTED 51975 PRIOR ARTINVENTOR VIVIAN EASTON BYM m ATTORNEY! PATENTEWR W5 3,719,844

SHEET 50F 5 INVENTOR ATTORNEYS VIVIAN EASTON W I 5w DYNAMO-ELECTRICMACHINES This invention relates to windings for dynamo'electric machinesand particularly, though not exclusively, to rotor windings suppliedwith d.c. excitation current and acting as field windings. In largealternating current generators of the turbogenerator type, and similarmachines such as synchronous compensators and synchronous motors, themost common winding arrangement is to have a multi-phase stator windingand a rotor winding supplied with d.c. excitation current, the latterproviding a rotating electric field for the machine. The form of windingin almost universal use for the rotors of such machines is a singlelayer winding known as a concentric coil winding.

The normal form of concentric coil winding, whilst offering advantagesin respect of its construction from mechanical considerations, can provedifficult to employ in certain arrangements of rotor windings such asthose designed for liquid cooling of the windingor the separateexcitation of sections of the winding.

The object of the present invention is to provide a winding for adynamo-electric machine which is a single layer winding of modifiedconcentric form and in which the above-mentioned difficulty issubstantially reduced or eliminated.

The invention consists in a rotor winding for a cylindrical air-gapdynamo-electric machine which winding is of concentric coil form woundon a rotor cor'e formed of magnetic material, each coil having slotembedded portions lying in axially extending slots formed in the rotorcore and end-connecting portions disposed beyond the ends of the slots,one or more conductors forming a coil being modified in shape where theextension from a slot embedded portion to an end-connecting portionoccurs in such a way that the radial depth of at least part of theend-connecting portion is less than the radial depth of the slotembedded portion.

The invention also consists in a rotor winding in accordance with thepreceding paragraph in which a rotor winding in which the end-connectingportions of at least two coils overlap one another in the radial sense.

The invention also consists in a rotor winding in accordance with eitherof the preceding two paragraphs adapted to be supplied with d.c.excitation current,

which rotor winding comprises at least two circum-- ferentiallydisplaced winding sections, each winding section being of concentriccoil form.

The invention also consists in a rotor winding in accordance with thepreceding paragraph in which at least one circumferentially extendinglayer of end-connecting portions of one winding section overlaps, asviewed radially of the rotor, at least part of one or more of thecircumferentially extending layers of end-connecting portions of anotherwinding section.

The invention also consists in a rotor winding in accordance with eitherof the two preceding paragraphs which winding is constituted by twoelectrically separate circumferentially displaced winding sections eachsection being adapted to be individually supplied by a separate sourceof d.c. excitation current.

The various features and advantages of the invention over conventionalconstructions can be better understood from the exemplary embodimentsdescribed hereinbelow and with reference to the accompanying drawings ofwhich:

FIG. 1 shows part of a developed diagram of a conventional concentriccoil form of winding for a dynamo-electric machine rotor;

FIG. 2 shows an end view of the conductors forming coil end-connectionsin the developed diagram of FIG. 1, looking in the direction of thearrow X on the latter Figure;

FIG. 3 shows, in simplified form an end elevation of a rotor winding ofthe form relating to FIGS. 1 and 2,

FIG. 4 shows part of a developed diagram of a modified concentric coilform of winding for a dynamoelectric machine rotor in accordance withthe present invention;

FIG. 5 shows an end view of the conductors forming coil end-connectionsin the developed diagram of FIG. 4, looking in the direction of thearrow Y on the latter Figure;

FIG. 6 shows, in simplified form an end elevation of a rotor winding ofthe form shown in FIGS. 4 and 5;

FIG. 7 shows a side elevation of a portion of the developed rotorwinding shown in FIGS. 4 and 5 looking in the direction of the arrow Zon FIG. 4;

FIG. 8 shows, in a similar side elevation to that of FIG. 7, analternative form of coil end-connection construction in accordance withthe invention to that shown in FIG. 7 for the winding shown in FIG. 4;

FIG. 9 shows, in simplified form, an end elevation of the rotor windingshown in FIG. 8; and

FIG. 10 shows, in simplified form, an end elevation of a further form ofrotor winding in accordance with the invention.

Referring first to FIG. 1, a conventional concentric coil form of rotorwinding is shown of the type commonly employed for largeturbo-generators. In the example shown here, there are 16 coil sides;and, a cylindrical rotor core of magnetic material provided with twogroups of eight slots, each slot containing only one coil side, would beprovided to carry the winding and form part of the magnetic circuit ofthe machine.

In the diagram shown in FIG. 1, eight coils a h are wound in two groupsof concentric coils, the four coils a d fonning one group and coils e hthe second group. Each coil has two coil side portions and two coilend-containing portions, only one end-connecting portion for each coilbeing shown. Thus, for example, coil a has two coil side portions a a(hereinafter referred to simply as coil sides), each located in aseparate core slot and an end-connecting portion a;, (hereinafterreferred to as an end-connection), the latter being situated outside ofthe rotor slot and forming part of the so-called overhang' of thewinding. The full length of the coil sides a, a is not indicated, forthe sake of simplicity, and a second end-connecting portion closing coila at the ends (not shown) of the coil sides remote from portion a; istherefore omitted from the diagram.

Each coil such as coil 0 may comprise a number of turns, say 4 turns,thus giving the same number of conductors in each slot, the conductorsusually being stacked radially above one another in a slot. Coil a maytherefore comprise 4 tums,-aa, a3, a7, a8, as is made clear by referenceto the end view shown in FIG. 2, where the four conductors comprisingthe end-connection a for coil a are shown, these conductors obscuringthe end-connection for coils b, c and d. The end connecting conductorsfor coil are given the references a 01, a 13, a 'y and a;,& in FIG. 2,and corresponding references are given for the end connecting portion cof coil e.

Each conductor may comprise a number of sub-conductors, sometimesreferred to as strands, but such sub-divisions of a conductor are notshown in any of the Figures accompanying this specification.

Passage of d.c. excitation current through the concentric group of coilsa, b, c, d in the direction of the arrows shown on the coil sides givesrise to a magnetic field in and about the rotor, a north (N) pole-faceresulting at the rotor surface between the coil sides d and d of coil d.Similarly, a south (S) pole-face is produced between coil sides h, andh,. The eight coil sides, comprising four coil sides from eachconcentric group, lying between each pair of pole-faces occupy a groupof eight adjacent slots at opposite sides of the rotor. The distributionof pole faces N and S in relation to the end-connections of the coils istherefore as shown in FIG. 3, the rotor being indicated generally byreference numeral 1. The electrical connections between the four coilsof each group of concentric coils are omitted to simplify the diagram,as also are the input and output connections to the winding and also thenormal series connection between the two groups.

It will be appreciated from the end view shown in FIG. 2 that the simpleconcentric coil arrangement shown gives limited access in the axialdirection to the inner concentric coils of each group, such as coils b,c and d, at the end-connections. In accordance with the presentinvention, a modified concentric coil arrangement, as shown in FIG. 4may be adopted giving improved access to the end-connections of a singlelayer winding where desired, for example, for providing individualexciting arrangements for separate sections of the winding.

Referring to FIG. 4, the rotor winding shown again comprises sixteencoil sides each of which is arranged to occupy a separate coil slot in acylindrical rotor core to form a single-layer winding. The windingdiffers from that shown in FIG. 1, however, in that it comprises twoseparate winding sections, A and B.

Each winding section comprises two groups of concentric coils, with twocoils in each group. Thus, section A comprises the group of twoconcentric coils Aa and Ab and the group of two concentric coils Ac andAd. The two coil sides of coil A0 are given the references Aa and An, inthe diagram, whilst the end connection has the reference Aa;,, andsimilar references are given to the remaining coils of the winding.

Winding section B is circumferentially spaced around the rotor fromsection A, as shown, so that four coil sides of section A, such as Ab AaAc, and Ad,,

and .four coil sides of section B, such as Bd Bc Ba,

and 8b,, lie in eight adjacent slots in the rotor surface. With d.c.excitation currents flowing in the directions indicated by the arrows,therefore, the N pole face produced by section A and given the referenceN in the diagram is circumferentially displaced from the N pole face N 8produced by section B, and similarly for the S pole faces S A and S Ifthe excitation current in each winding section is the same, theresultant pole faces N and S due to the whole winding would be in thepositions shown, but their positions may be controllably varied within asector of the rotor by varying the excitation currents in the separatewinding sections.

It is clear from a consideration of FIG. 4 that there must be crossingover, as viewed radially of the rotor, of the end-connections of thecoils in section A and section B. In order to enable the end-connectionsto be made within a radial depth which does not exceed and may be lessthan the depth of a coil side in a rotor core slot, therefore, theend-connections are made flatter and wider than the side portions of acoil in windings according to the present invention. This is indicatedin the diagram of FIG. 4 by drawing the end connection portions, such asAb A0 etc., as shaded strips, whilst the coil side portions such as Adg,Ac etc., are shown as single lines.

The end-connections Aa Ab Ac and Ad of winding section A need not beaxially spaced from the endconnections Ba Bb Bc and Bd as shown in FIG.4, but are preferably disposed to overlap each other in the radialdirection. Thus end-connection Ab may overlap parts of end-connectionsBd and Bb and end-connection Aa may overlap parts of end-connections B0and Ba The modification in conductor shape where the conductors of acoil pass from a side portion to an end-connecting portion are madeclearer by reference to FIGS. 5 7, where four conductors per coil sideare shown as an example. The four conductors of a coil side are giventhe sub-references a, B, y, 8, in order from the uppermost to thelowermost conductor in a rotor slot in FIGS. 5 7 and also the subsequentFigures of the drawings.

As shown in FIG. 5, the end-connection Aa which obscures end-connectionAb in this view, is composed of four conductors Aa a, Aa fi, Aa 7 and Aa8 which may each be somewhat less than half the thickness ofend-connections for a conventional concentric winding as shown in FIG. 2wound in rotor slots of the same depth. The end elevation of FIG. 6 issimilar to that of FIG. 3 for the conventional concentric winding, butshows the distribution of the resultant pole faces N and S for themodified winding shown in FIG. 4 if winding sections A and B have thesame excitation current.

FIG. 7 shows how the conductors of a coil side are modified in shape inpassing to an end-connection so that the end-connections of a coil ofone winding section may lie in a circumferential layer overlapping, in aradial sense, the end-connections of a coil in the other windingsection. The view is taken circumferentially around the rotor asindicated by the arrowed line Z in FIG. 4, considering end-connection Abto overlap endconnection Bb in the radial sense, that is to say, thesetwo end-connections not being axially displaced from one another aswould appear from the diagram of FIG. 4. 4

In FIG. 7 the radial depth of a coil side is indicated by reference T,and the radial depth of each of its four conductors by t,. The radialdepth of the coil end-connections is T and that of the individualconductors in the end-connections is t,.. As shown, conductors Bb a,Bbfi, Bb 'y and Bb,6 in coil side Bb are flattened so that theirthickness decreases from t, to r and at the same time are bent downwardsso that their continuations in end-connection Bb stack into acircumferential layer of radial depth T somewhat less than half T,.Similarly conductors Ab a, AM, Ab 'y and Ab fi in coil side Ab (hiddenby side Bb in FIG. 7) are flattened and .bent upwards to stack into acircumferential layer, forming end-connection Ab lying radially aboveend-connection Bb and overlapping part of it. In addition to beingflattened, the conductors may be widened to maintain theircross-sectional area the same or substantially so. A layer of insulation1 between the end-connections of sections A and B is required, as shown.

Referring again to FIG. 5, it is clear that the winding described withreference to FIGS. 4 7 allows ready access to four coil end-connectionsas opposed to only two in the winding shown in FIGS. 1 3, whilst eachwinding contains a total of eight coils wound in a single layer in therotor slots. The construction of the modified concentric coil winding inaccordance with the invention hence simplifies the making ofend-connections to winding sections A and B to allow these sections tobe excited independently.

The conductors of a coil-side need not all be formed into onethinnercircumferential layer in the coil endconnections, but mayalternatively be formed into two or more layers of different meansdiameters. In FIG. 8, for example, which is a similar view to that shownin FIG. 7, the conductors forming coil side Bb are formed into twocircumferential layers, these being an outer layer formed ofend-connection conductors Bb a and B12 13, and an inner layer formed ofend-connection conductors Bb 'y and Bb 8. The conductors of coil side Abare similarly formed into two layers in the end-connection, and arestacked alternately with the two layers of end-connection Bb threeinsulating layers 2, 3 and 4 being required, as shown. The end elevationof this modification is shown in FIG. 9.

In a further alternative form of construction for the end-connections,shown in end elevation only in FIG. 10, the conductors of coil sides inone winding section, say section A, may be formed into twocircumferential layers of different mean diameter in theend-connections, whilst the conductors of coil sides in the othersection B may be formed into a single circumferential layer lyingbetween the end-connection layers of winding A. This arrangement hasconsiderable constructional advantage in that the center insulationlayer 3 of the arrangement shown in FIG. 8 is no longer required andthat for each end-connection layer there is one coil conductor which hasone face which is not radially displaced between its coil side'positionand end-connec' tion position. With regard to the latter advantage, itwill be noted that in the construction shown in FIG. 8 the lower face ofconductor Bb and the upper face of conductor Ab 'y are'slightlydisplaced from the faces of the conductors as they lie in the coil sidesto allow insulation layer 3 to be positioned between them.

Whilst in the embodiments of the invention described the two windingsections each occupy half the number of slots of a conventionalconcentric coil winding wound in the same number of rotor slots, theinvention is not restricted to such arrangements. In a two-pole rotorhaving 16 slots, for example, one windin section may occupy six slotsand the other ten slots.

e invention is not limited to two-pole field windings, but may beapplied in field windings having more than two-poles.

Whilst in the embodiment of the invention described with reference toFIGS. 4-10, the conductors of a coil are reduced in radial height at theend-connection to somewhat less than one half their slot embedded depth,the invention is not limited to windings where the reduction in radialheight is of the order of one half. Moreover, the portions of conductorwhich are reduced in radial dimension in the end connections need notnecessarily be modified in width to an extent necessary to maintaintheir cross-sectional area of the same order throughout a coil.

I claim:

1. A rotor field winding for a cylindrical airgap dynamo-electricmachine, comprising a plurality of slot-embedded windings of concentricform wound on a rotor core of magnetic material and disposed in axiallyextending slots in said rotor core, wherein each said winding includes aplurality of coils formed concentrically about a polar axis, said coilsbeing wound out of a conductor and including end connecting portions forcoil-interconnection disposed beyond ends of said axially extendingslots, said end connecting portions including circumferentiallyextending portions, said rotor field winding characterized in that atleast part of the conductor in said end connecting portions is formed tohave a radial depth less than a corresponding radial conductor depth ina slot embedded region, and, said circumferentially extending portion ofat least one coil is disposed to overlap in the radial sense thecircumferentially extending portion of at least one of the remainingcoils, thereby providing direct axial access to the ends of inner coilsof the concentric form windings.

2. A rotor field winding as claimed in claim 1, wherein said pluralityof slot-embedded windings are provided in the form of two separatelyexcitable circumferentially displaced winding sections each sectionbeing of concentric coil form and wound about a separate polar axis andwherein said circumferentially extending portion of at least one coil ofone of said winding sections is arranged to overlap in the radial sensethe circumferentially extending portion of at least one of the coils ofthe second winding section, the polar axes of the two winding sectionsbeing in different axial planes.

1. A rotor field winding for a cylindrical airgap dynamoelectricmachine, comprising a plurality of slot-embedded windings of concentricform wound on a rotor core oF magnetic material and disposed in axiallyextending slots in said rotor core, wherein each said winding includes aplurality of coils formed concentrically about a polar axis, said coilsbeing wound out of a conductor and including end connecting portions forcoil-interconnection disposed beyond ends of said axially extendingslots, said end connecting portions including circumferentiallyextending portions, said rotor field winding characterized in that atleast part of the conductor in said end connecting portions is formed tohave a radial depth less than a corresponding radial conductor depth ina slot embedded region, and, said circumferentially extending portion ofat least one coil is disposed to overlap in the radial sense thecircumferentially extending portion of at least one of the remainingcoils, thereby providing direct axial access to the ends of inner coilsof the concentric form windings.
 1. A rotor field winding for acylindrical airgap dynamo-electric machine, comprising a plurality ofslot-embedded windings of concentric form wound on a rotor core oFmagnetic material and disposed in axially extending slots in said rotorcore, wherein each said winding includes a plurality of coils formedconcentrically about a polar axis, said coils being wound out of aconductor and including end connecting portions for coil-interconnectiondisposed beyond ends of said axially extending slots, said endconnecting portions including circumferentially extending portions, saidrotor field winding characterized in that at least part of the conductorin said end connecting portions is formed to have a radial depth lessthan a corresponding radial conductor depth in a slot embedded region,and, said circumferentially extending portion of at least one coil isdisposed to overlap in the radial sense the circumferentially extendingportion of at least one of the remaining coils, thereby providing directaxial access to the ends of inner coils of the concentric form windings.